This invention relates to a tilt mechanism for marine propulsion devices and more particularly to an improved tilt and trim unit for an outboard drive.
As is well known, outboard drives such as outboard motors and the outboard drive unit of an inboard-outboard assembly are normally pivotal about a horizontally disposed axis. Pivotal movement about this axis is employed to provide a trim adjustment for the position of the outboard drive and also so as to permit the outboard drive to be tilted up clear of the water. For convenience, it has been proposed to employ hydraulic arrangements for moving the outboard drive both through the trim adjustment and also for tilting the outboard drive up out of the water. Many of these hydraulic tilt and trim assemblies use a trim cylinder having a piston that engages a portion of the outboard drive and is effective to pivot it through a small range of trim adjustment positions. A further hydraulic cylinder is normally employed and which is generally connected to both the transom of the watercraft and to the outboard drive for raising the outboard drive to a tilted up position. From the nature of the prior art arrangements, it is necessary to have the piston rod of the trim cylinder in mere abutting relationship with the outboard drive. As a result, there is a likelihood of relative movement between the drive and the piston rod, particularly when it is in its extreme positions, which can result in noise, wear and other associated problems.
To overcome such problems, the applicant of this invention has disclosed a tilting/trimming device having a single cylinder assembly with two separate hydraulically separated cylinder bores in which separate pistons are supported for reciprocation. Each piston has a piston rod that is directly connected to a corresponding element of the outboard drive so as to insure against any wear or play in the system and to afford a compact assembly (See Japanese Examined Patent Publication HEI2-5637).
However, since the device disclosed in HEI2-5637 employs two independent trimming and tilting cylinders, each with an upper and a lower chamber, it has been necessary to connect hydraulic pipings to all four of the upper and lower chambers of the device, and a complicated hydraulic operating circuit has been required.
Furthermore, with a trim and tilt device wherein both operations are carried out with a single cylinder, it has generally been necessary to carry out the slower trimming procedure before moving on to the relatively quicker tilting operation. Thus, it generally has not been possible to bypass altogether a trimming step and to quickly tilt an engine when it is not desirable to trim it.
It is, therefore, a principal object of this invention to provide an improved tilt and trim unit for a marine drive.
It is a further object of this invention to provide an improved and simplified tilt and trim unit, and associated hydraulic circuit, that will not result in the generation of noise and in which wear is minimized.
It is still a further object of the invention to provide a simplified tilt and trim unit allowing an operator to quickly tilt a drive unit, bypassing any trimming step where such a step is not necessary or desirable.